A keyboard instrument is a musical instrument played using a keyboard. A piano (e.g., an acoustic piano) is a typical keyboard instrument. The piano may include a protective case, a soundboard, metal strings, hammers, keys (e.g., white keys and black keys), and pedals. Each key may be mechanically connected to a hammer, which is constructed to strike a metal string(s). When a key of the acoustic piano is pressed by a player, the corresponding hammer may strike the corresponding metal string(s). Excited by the strike, the string(s) may respond with vibrations with various frequencies. These vibrations may be transmitted to the soundboard. Those that have the same frequencies of the resonant frequency of the soundboard may be amplified by coupling the acoustic energy to the air. When a pedal of the piano (e.g., a sustain pedal) is applied, the metal string may keep vibrating until internal and external damping forces of the metal string gradually consume the vibration energy. Accordingly, a note produced by the piano may be sustained even when the keys are released.